Aluminum nitride (AlN) crystal has a wide energy bandgap of 6.2 eV and a high thermal conductivity of approximately 3.3 WK−1 cm−1, and has high electrical resistance as well. AlN crystal and other nitride semiconductor crystals have therefore drawn attention as substrate materials for semiconductor devices such as optical devices and electronic devices. For the method whereby such nitride semiconductor crystal is grown, sublimation method, for example, is employed (e.g., Patent Reference 1, Non-Patent Reference 1).
Non-Patent Reference 1 sets forth implementing the following steps. At first an AlN crystal source material is emplaced into a crucible made of carbon. Next, the carbonous crucible is heated to a temperature at which the source material sublimes. By subliming the source material the heating generates sublimation gases, enabling the growth of minute AlN crystal at a powdered or particulate level.
Meanwhile, Patent Reference 1 sets forth manufacturing nitride single crystal by means of the following manufacturing apparatus (e.g., FIG. 4). Namely, the manufacturing apparatus is furnished with an induction heating coil that is a heating means, a heating reactor body disposed to the inside of the induction heating coil, and a crucible, disposed in the lower part of the interior of the heating reactor body, that holds nitride single-crystal source material. The crucible is stated to be made of graphite.
Thus, the above-cited Non-Patent Reference 1 and Patent Reference 1 set forth that in growing nitride semiconductor crystal, a carbonous crucible is employed. Withstanding high temperatures in excess of 2000° C. is stated as the reason why carbon is chosen for the crucible.